Method for manufacturing a composite wire

ABSTRACT

One aspect relates to a method for manufacturing a composite wire, including providing a first part in form of a rod, providing a second part in form of a tube surrounding the rod at least partially to form a rod-tube assembly, providing a clad part in form of a cylinder surrounding the rod-tube assembly at least partially to form a cladded rod-tube assembly, and extruding the cladded rod-tube assembly to form the composite wire. The second part includes an alloy comprising the following alloy components:
         a) Cr in the range from about 10 to about 30 wt. %;   b) Ni in the range from about 20 to about 50 wt. %;   c) Mo in the range from about 2 to about 20 wt. %;   d) Co in the range from about 10 to about 50 wt. %;   wherein the Al content of the alloy is less than about 0.01 wt. %;   wherein each wt. % is based on the total weight of the alloy.

CROSS-REFERENCE TO RELATED APPLICATION

This Utility patent application claims priority to Application No. 62/519,749 filed on Jun. 14, 2017 and application No. EP 17175926.9, filed on Jun. 14, 2017, each of which are incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is also related to Patent Application Ser. No. 62/519,719 filed on Jun. 14, 2017, entitled “COMPOSITE WIRE” having Attorney Docket No. H683.157.101/P12991 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “COMPOSITE WIRE” having Attorney Docket No. H683.157.102/P12991 US01; Patent Application Ser. No. 62/519,779 filed on Jun. 14, 2017, entitled “METHOD FOR MANUFACTURING A CABLE” having Attorney Docket No. H683.159.101/P12996 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “METHOD FOR MANUFACTURING A CABLE” having Attorney Docket No. H683.159.102/P12996 US01; Patent Application Ser. No. 62/519,823 filed on Jun. 14, 2017, entitled “METHOD FOR MANUFACTURING A PASSIVATED PRODUCT” having Attorney Docket No. H683.160.101/P12998 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “METHOD FOR MANUFACTURING A PASSIVATED PRODUCT” having Attorney Docket No. H683.160.102/P12998 US01; Patent Application Ser. No. 62/269,268 filed on Dec. 18, 2015, entitled “ALLOY COMPRISING CR, NI, MO AND CO FOR USE IN MEDICAL DEVICES” having Attorney Docket No. H685.104.101/HU12121US PR; and patent application Ser. No. 15/382,294 filed on Dec. 16, 2016, entitled “CR, NI, MO AND CO ALLOY FOR USE IN MEDICAL DEVICES” having Attorney Docket No. H685.104.102/HU12121US.

BACKGROUND

One aspect relates to a method for manufacturing a composite wire, a composite wire manufactured by such method, and a medical device including such composite wire. The composite wire includes an alloy including Cr, Ni, Mo and Co, with tightly controlled levels of impurities.

Much investigation in recent years has been directed to a search for new high performance alloys, particularly for medical applications where a very high value is placed on reliability and materials are required which exhibit a low failure rate even over a long time period.

Cardiac Pacemakers, Implantable Cardioverter Defibrillation Devices and Cardiac Resynchronization Devices are applications where reliability is particularly important, especially in terms of resistance to physical fatigue and to chemical corrosion. Invasive surgery is required to implant a pacemaker into the body or remove or replace parts, and it is highly desirable for the individual components of the pacemaker to have a long working life in order to reduce the requirement for surgical intervention. Furthermore, it is desirable for the working life to have a low variance. In a heart pacemaker, one component which is exposed to a particularly high amount of stress during normal operation is the so called lead which connects the implantable pulse generator to the heart tissue. A flexible lead is required in order to connect the implantable pulse generator to the heart tissue without imposing undue physical stress on the heart and the lead flexes during normal operation, typically repetitively with a frequency on the order of that of a human heart beat. A high resistance to fatigue is therefore required in the lead in order to withstand frequent physical stress over a long period of time. A high resistance of the lead to corrosion is important not only in terms of the lifetime of the component, but also in terms of reducing toxicity to the body.

WO 2005026399 A1 discusses an approach to improving the properties of an alloy by reducing the content of titanium nitride and mixed metal carbonitride.

US 2005/0051243 A1 focuses on alloys with a reduced content of nitrogen.

A manufacturing of composite wires comprising two different metals or alloys may include a drawing of a tube of metal 1 on a rod of metal 2 with metal 1 at the outside volume of the wire and metal 2 at the inside volume of the wire. A straight drawing of such assembly may be conducted and repeated with dies of subsequently reduced die diameter.

Disadvantages of such manufacturing of a composite wire may include a limited lot size due to a maximum length of conventional drawing benches, tensile stresses created during the wire drawing that may not lead to a sufficient compression of metal 1 (outer volume) on metal 2 (inner volume), a bonding of metal 1 to metal 2 may not be continuous, brittle intermetallic phases may develop at an interface of the different metals and may be root causes for early fatigue failures.

For these and other reasons, a need exists for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments, and which are not to be considered as limiting the scope. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

FIG. 1 shows schematically a lead according to one embodiment.

FIG. 2 shows schematically an apparatus for measuring fatigue resistance.

FIG. 3 shows schematically a pacemaker comprising a lead according to one embodiment.

FIG. 4 shows a cross sectional image of a wire of material according to example 2 (comparative).

FIG. 5 shows a cross sectional image of a wire of material according to example 2 (comparative).

FIG. 6 shows an analysis of elemental composition by energy dispersive x-ray spectroscopy of an inclusion in a wire of material according to example 2 (comparative).

FIG. 7 shows a cross sectional image of a wire of material according to example 2 (comparative).

FIG. 8 shows a cross sectional image of a wire of material according to example 2 (comparative).

FIG. 9 shows a cross sectional image of a wire of material according to example 2a (comparative) with an Ag core.

FIG. 10 shows a cross sectional image of a wire of material according to example 2a (comparative) with an Ag core.

FIG. 11 shows an analysis of elemental composition by energy dispersive x-ray spectroscopy of an inclusion in a wire of material according to example 2a (comparative) with an Ag core.

FIG. 12 shows a plot of fatigue results for a wire of material according to example 1 (inventive) and a wire of material according to example 2 (comparative).

FIG. 13 shows a plot of fatigue results for a wire of material according to example 1a (inventive) with an Ag core and a wire of material according to example 2a (comparative) with an Ag core.

FIG. 14 shows a method for manufacturing a composite wire.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the embodiments may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present embodiments. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present embodiments is defined by the appended claims.

It is to be understood that the features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise.

One embodiment provides an improved and for example more flexible manufacturing method for a composite wire.

It should be noted that the aspects of the embodiments described in the following apply also to the method for manufacturing a composite wire, the composite wire manufactured by such method, and the medical device comprising such composite wire.

According to one embodiment, a method for manufacturing a composite wire is presented. The method for manufacturing the composite wire includes the following steps, not necessarily in this order:

-   -   providing a first part in form of a rod,     -   providing a second part in form of a tube surrounding the rod at         least partially to form a rod-tube assembly,     -   providing a clad part in form of a cylinder surrounding the         rod-tube assembly at least partially to form a cladded rod-tube         assembly, and     -   extruding the cladded rod-tube assembly to form the composite         wire.

The first part or the second part includes an alloy comprising the following alloy components:

a) Cr in the range from about 10 to about 30 wt. %; b) Ni in the range from about 20 to about 50 wt. %; c) Mo in the range from about 2 to about 20 wt. %; d) Co in the range from about 10 to about 50 wt. %.

The Al content of the Cr, Ni, Mo and Co alloy is less than about 0.01 wt. % and each wt. % is based on the total weight of the alloy.

One embodiment refers to an extrusion process that joints at least two different materials. A composite wire may be understood as a wire comprising at least two different materials. One of these materials is the Cr, Ni, Mo and Co alloy described above. The other material may be different to this alloy. It can be a metal or another alloy. A wire may be a single strand or rod of metal or may include a bundle of such strands or rods. The wire may be configured to bear mechanical loads or electricity and/or telecommunications signals. The wire may be flexible and may be circular in cross-section or square, hexagonal, flattened, rectangular or the like.

The Cr, Ni, Mo and Co alloy may be an alloy, which has improved resistance to physical fatigue, a high corrosion resistance and/or the ability to be drawn into a thin wire. In an example, the Cr, Ni, Mo and Co components are major constituents of the Cr, Ni, Mo and Co alloy with at least about 95 wt. % of the alloy being Cr, Ni, Mo and Co. Details in view of the alloy are provided further below.

In contrast to a conventional manufacturing of composite wires based on wire drawing, an extrusion process according to one embodiment is generally more cost efficient and allows a larger ratio of area prior to and post deformation. The extrusion process allows an increased lot size because it is not limited to the size of a drawing bench and thereby allows a better scalability. A direct contact of the different materials is enabled, which ensures a continuous bonding among these materials. Adhesion and joint of different materials, even with different melting points, are greatly improved.

The first part may form an inner volume of the composite wire and the second part may form an outer volume of the composite wire. It can be said the first part is a rod, solid cylinder, filler or core for a longitudinal recess in a hollow tube forming the second part. When seen in a cross section, a filling ratio between an area of the first part (filler) and an area of the second part (hollow tube) may be between 5 and 75 percent, in one embodiment, between 10 and 60 percent, in one embodiment, between 15 and 45 percent, and even in one embodiment, between 20 and 30 percent.

In an example, the second part includes the Cr, Ni, Mo and Co alloy. The second part may be made of MP35N, in one embodiment, annealed MP35N, and in one embodiment, fully annealed MP35N. Further details to the alloy are provided further below. The second part in form of a tube may entirely surround the rod to form the rod-tube assembly.

In an example, the first part includes a metallic material. The metallic material may be a metal or an alloy. The material of the first part may be biocompatible. In an example, the first part includes at least one of a group of Silver, Platinum, Tantalum, Gold, Copper and alloys thereof. The first part may include at least one of a group of: Platinum, a Platinum based alloy, a Platinum-Iridium alloy, a Platinum-Tungsten alloy, Gold, a Gold alloy, Tantalum, Titanium, a Titanium-Molybdenum alloy, and a Titanium Aluminum Vanadium alloy. The first part may include a Platinum-Iridium alloy with about 70-90 wt. % Platinum and 10-30 wt. % Iridium.

Of course, also the first part may include the Cr, Ni, Mo and Co alloy and the second part may include the metallic material. Everything described herein analogously applies to this alternative.

The clad part may be a cover that can be configured to reduce friction during extrusion. In an example, the clad part includes a material with a lower friction coefficient than the material of the second part. In an example, the clad part includes Copper. The clad part may be made of pure Copper and in one embodiment, out of fully annealed Copper. The clad part in form of a cylinder may entirely surround the rod-tube assembly to form a cladded rod-tube assembly.

The first part, the second part and/or the clad part may be made out of stock material and for example machined out of stock material. The second part may be drilled out of stock material. The clad part may be made out of a material sheet, which is for example rolled into a cylindrical shape.

The extrusion may provide an extrusion ratio defined as starting cross-sectional area divided by a cross-sectional area of the final extrusion in the range of 5 to 25, in one embodiment, 10 to 20, in one embodiment, 14 to 18.

The extrusion can be done with the material(s) hot or cold. In an example, the method for manufacturing the composite wire further includes a heating of the cladded rod-tube assembly before the extrusion step. The heating may be a pre-heating. Time is minimized when the materials are at high temperature, which reduces the time for diffusion and thereby a potential formation of brittle intermetallic phases.

In an example, the method for manufacturing the composite wire further includes an application of vacuum of the cladded rod-tube assembly before the extrusion step. The vacuum may include vacuum and low pressure. It may be in the range of 10⁻¹ to 10⁻³ mbar and in one embodiment, about 10⁻² mbar. The heating and the vacuum may be applied simultaneously. The heating and/or the vacuum may be applied in an inert atmosphere.

In an example, the method for manufacturing the composite wire further includes a removing of the clad part after the extrusion step. In an example, the removing of the clad part is an etching-off. The removing of the clad part may be done right after the extrusion or later in the process before an annealing step.

In an example, the method for manufacturing the composite wire further includes a wire drawing of the composite wire after the extrusion step. The wire drawing leads to a reduction of the composite wire diameter. The wire drawing can be repeated if necessary.

In an example, the method for manufacturing the composite wire further includes a deforming of the composite wire into a coil. The deformation may be done e.g. after extrusion or after wire drawing. The deformation may be done e.g. before the removing of the clad part.

In an example, the method for manufacturing the composite wire further includes an annealing of the composite wire after the etching-off step to soften the materials.

The method for manufacturing a composite wire may further include a providing of a third part in form of a tube surrounding the second part at least partially to form a rod-tube assembly, which will then be surrounded at least partially by the clad part to form a cladded rod-tube assembly, which will then be extruded to form the composite wire. The method for manufacturing a composite wire may include even further steps of providing further parts to form a composite wire of more than two or more than three materials. The material may differ from at least one or both of its adjacent material or even from all materials provided in the composite wire.

According to one embodiment, also a composite wire manufactured by the method as described above is presented. The composite wire may be a semi-finished or finished product used for medical applications such as coils or strands used for e.g. cardiac rhythm management.

In contrast to a conventional composite wire made by wire drawing, the extruded composite wire according to the one embodiment allows an increased and continuous bonding of the different materials at their interface that makes the composite wire more robust during a subsequent wire drawing and during operation. The composite wire according to one embodiment is covered or cladded not by conventional drawing a tube on a rod, but by extrusion. This promotes adhesion of different materials, for example metals and alloys, due to high compressive and shear stresses at an interface of the different materials. This way, also metals and alloys with significantly different melting points can be joint.

A diameter of the composite wire may be in a range of 10 to 500 μm. At least two composite wires may be wound into a coil or stranded into a cable.

According to one embodiment, also a medical device comprising a composite wire as described above as a lead is presented. The medical device may be a pacemaker, an implantable cardioverter defibrillator, a cardiac resynchronization device, a neuromodulation device, a cochlea implant or any other implantable stimulation device comprising a composite wire as described above as a lead.

The Cr, Ni, Mo and Co alloy may be an alloy, which has improved resistance to physical fatigue, a high corrosion resistance, and/or which can be drawn into a thin wire, in one embodiment, less than about 50 μm. The composite wire according to one embodiment may be a wire having comparable tensile properties to known wires, but for which the proportion of outlying failures in fatigue resistance is reduced.

A contribution to achieving at least one of the above described objects is made by the following embodiments of the Cr, Ni, Mo and Co alloy (in the following “alloy”).

-   |1| An alloy comprising the following alloy components:     -   a) Cr in the range from about 10 to about 30 wt. %, in one         embodiment, in the range from about 15 to about 25 wt. %, in one         embodiment, in the range from about 19 to about 21 wt. %;     -   b) Ni in the range from about 20 to about 50 wt. %, in one         embodiment, in the range from about 30 to about 45 wt. %, in one         embodiment, in the range from about 33 to about 37 wt. %;     -   c) Mo in the range from about 2 to about 20 wt. %, in one         embodiment, in the range from about 5 to about 15 wt. %, in one         embodiment, in the range from about 9 to about 10.5 wt. %;     -   d) Co in the range from about 10 to about 50 wt. %, in one         embodiment, in the range from about 20 to about 40 wt. %, in one         embodiment, in the range from about 33 to about 37 wt. %;     -   wherein the Al content of the alloy is less than about 0.01 wt.         %, in one embodiment, less than about 0.005 wt. %, in one         embodiment, less than about 0.001 wt. %;     -   wherein each wt. % is based on the total weight of the alloy. -   |2| The alloy according to embodiment |1|, wherein the content of Mg     is less than about 0.005 wt. %, in one embodiment, less than about     0.0001 wt. %, in one embodiment, less than about 0.00001 wt. %,     based on the total weight of the alloy. -   |3| The alloy according to embodiment |1| or |2|, wherein the     content of Ca is less than about 0.005 wt. %, in one embodiment,     less than about 0.0001 wt. % in one embodiment, less than about     0.00001 wt. %, based on the total weight of the alloy. -   |4| The alloy according to any of the preceding embodiments, wherein     the content of Ce is less than about 0.005 wt. %, in one embodiment,     less than about 0.0001 wt. % in one embodiment, less than about     0.00001 wt. %, based on the total weight of the alloy. -   |5| The alloy according to any of the preceding embodiments, wherein     the content of Ti is less than about 0.1 wt. %, in one embodiment,     less than about 0.01 wt. % in one embodiment, less than about 0.001     wt. %, further in one embodiment, less than about 0.0005 wt. %,     based on the total weight of the alloy. -   |6| The alloy according to any of the preceding embodiments, wherein     the content of Fe is in the range from about 0.0001 to about 1 wt.     %, in one embodiment, in the range from about 0.0005 to about 0.1     wt. %, in one embodiment, in the range from about 0.001 to about     0.05 wt. %, based on the total weight of the alloy. -   |7| The alloy according to any of the preceding embodiments, wherein     at least one of the following is satisfied:     -   a) The content of C in the alloy is less than about 0.1 wt. %,         in one embodiment, less than about 0.08 wt. % in one embodiment,         less than about 0.05 wt. %     -   b) The content of B in the alloy is less than about 0.01 wt. %,         in one embodiment, less than about 0.001 wt %, in one         embodiment, less than about 0.0002 wt. %;     -   c) The content of P in the alloy is less than about 0.01 wt. %,         in one embodiment, less than about 0.005 wt. %, in one         embodiment, less than about 0.001 wt. %, further in one         embodiment, less than about 0.0005 wt. %;     -   d) The content of S in the alloy is less than about 0.005 wt. %,         in one embodiment, less than about 0.003 wt. %, in one         embodiment, less than about 0.002 wt. %, further in one         embodiment, less than about 0.0008 wt. %;     -   each wt. % being based on the total weight of the alloy. In         aspects of this embodiment, the combination of the above         criteria which are satisfied is selected from the group         consisting of: a), b), c), d), a)+b), a)+c), a)+d), b)+c),         b)+d), c)+d), a)+b)+c), a)+b)+d), a)+c)+d), b)+c)+d) and         a)+b)+c)+d). -   |8| The alloy according to any of the preceding embodiments, wherein     at least one of the following is satisfied:     -   a) The content of Mn in the alloy is less than about 0.05 wt. %,         in one embodiment, less than about 0.005 wt. %, in one         embodiment, less than about 0.001 wt. %;     -   b) The content of Si in the alloy is less than about 0.05 wt. %,         in one embodiment, less than about 0.03 wt. %, in one         embodiment, less than about 0.02 wt. %;     -   each wt. % being based on the total weight of the alloy. In         aspects of this embodiment, the combination of the above         criteria which are satisfied is selected from the group         consisting of: a), b), a)+b). -   |9| The alloy according to any of the preceding embodiments, wherein     at least one of the following is satisfied:     -   a) The content of 0 in the alloy is in the range from about         0.0001 to about 0.05 wt. %, in one embodiment, in the range from         about 0.0001 to about 0.03 wt. %, in one embodiment, in the         range from about 0.0001 to about 0.01 wt. %;     -   b) The content of N in the alloy is in the range from about         0.0001 to about 0.01 wt. %, in one embodiment, in the range from         about 0.0001 to about 0.008 wt. %, in one embodiment, in the         range from about 0.0001 to about 0.005 wt. %;     -   each wt. % being based on the total weight of the alloy. In         aspects of this embodiment, the combination of the above         criteria which are satisfied is selected from the group         consisting of: a), b), a)+b). -   |10| The alloy according to any of the preceding embodiments,     wherein at least one of the following is satisfied:     -   a) The alloy contains less than about 0.01 wt. %, in one         embodiment, less than about 0.005 wt. %, in one embodiment, less         than about 0.001 wt. %, O in the form of a magnesium oxide;     -   b) The alloy contains less than about 0.01 wt. %, in one         embodiment, less than about 0.005 wt. %, in one embodiment, less         than about 0.001 wt. %, O in the form of an aluminium oxide;     -   c) The alloy contains less than about 0.01 wt. %, in one         embodiment, less than about 0.005 wt. %, in one embodiment, less         than about 0.001 wt. %, O in the form of a cerium oxide.     -   d) The alloy contains less than about 0.01 wt. %, in one         embodiment, less than about 0.005 wt. %, in one embodiment, less         than about 0.001 wt. %, O in the form of a calcium oxide.     -   e) The alloy contains less than about 0.01 wt. %, in one         embodiment, less than about 0.005 wt. %, in one embodiment, less         than about 0.001 wt. %, O in the form of a chromium oxide.     -   In aspects of this embodiment, the combination of the above         criteria which are satisfied is selected from the group         consisting of: a), b), c), d), a)+b), a)+c), a)+d), b)+c),         b)+d), c)+d), a)+b)+c), a)+b)+d), a)+c)+d), b)+c)+d),         a)+b)+c)+d), e), a)+e), b)+e), c)+e), d)+e), a)+b)+e), a)+c)+e),         a)+d)+e), b)+c)+e), b)+d)+e), c)+d)+e), a)+b)+c)+e),         a)+b)+d)+e), a)+c)+d)+e), b)+c)+d)+e) and a)+b)+c)+d)+e). -   |11| A process for the preparation of an alloy comprising the     following preparation steps:     -   a) Provision of a mixture comprising the following components:     -   i. Cr in the range from about 10 to about 30 wt. %, in one         embodiment, in the range from about 15 to about 25 wt. %, in one         embodiment, in the range from about 19 to about 21 wt. %;     -   ii. Ni in the range from about 20 to about 50 wt. %, in one         embodiment, in the range from about 25 to about 40 wt. %, in one         embodiment, in the range from about 33 to about 37 wt. %;     -   iii. Mo in the range from about 2 to about 20 wt. %, in one         embodiment, in the range from about 5 to about 15 wt. %, in one         embodiment, in the range from about 9 to about 10.5 wt. %;     -   iv. Co in the range from about 10 to about 50 wt. %, in one         embodiment, in the range from about 20 to about 40 wt. %, in one         embodiment, in the range from about 33 to about 37 wt. %.     -   wherein each wt. % is based on the total weight of the mixture         prepared for melting;     -   b) Melting the mixture in a vacuum induction melting step in         order to obtain a first melt, in one aspect of this embodiment,         one or more further vacuum induction melting steps are carried         out;     -   c) Solidifying the first melt in order to obtain a first solid;     -   d) Melting the first solid in a vacuum arc melting step in order         to obtain a further melt;     -   e) Solidifying the further melt in order to obtain a further         solid. -   |12| The process according to embodiment |11|, wherein pressure in     step b) is below about 0.1 bar, in one embodiment, below about 0.05     bar, in one embodiment, below about 0.01 bar. -   |13| The process according to embodiment |11| or |12|, wherein the     leak rate in step b) is below about 0.1 bar/min, in one embodiment,     below about 0.05 bar/min, in one embodiment, below about 0.01     bar/min. -   |14| The process according to any of the embodiments |11| to |13|,     wherein the pressure in step d) is below about 0.05 bar, in one     embodiment, below about 0.01 bar, in one embodiment, below about     0.005 bar. -   |15| The process according to any of the embodiments |11| to |14|,     wherein the leak rate in step d) is below about 0.05 bar/min, in one     embodiment, less than about 0.01 bar/min, in one embodiment, less     than about 0.005 bar/min. -   |16| The process according to any of the embodiments |11| to |15|,     further comprising a homogenization step carried out at a     temperature in the range from about 900 to about 1300° C., in one     embodiment, in the range from about 1000 to about 1250° C., in one     embodiment, in the range from about 1100 to about 1225° C. -   |17| The process according to any of the embodiments |11| to |16|,     further comprising a cogging step carried out at a temperature in     the range from about 900 to about 1300° C., in one embodiment, in     the range from about 1000 to about 1250° C., in one embodiment, in     the range from about 1100 to about 1225° C. -   |18| The process according to any of the embodiments |11| to |17|,     further comprising a finish roll step carried out at a temperature     in the range from about 900 to about 1300° C., in one embodiment, in     the range from about 1000 to about 1250° C., in one embodiment, in     the range from about 1100 to about 1225° C. -   |19| The process according to any of the embodiments |11| to |18|,     further comprising a straightening step. In one aspect of this     embodiment, the straightening is a hot straightening, in one     embodiment, carried out at a temperature in the range from about 900     to about 1200° C., in one embodiment, in the range from about 950 to     about 1100° C., in one embodiment, in the range from about 1000 to     about 1075° C. In one aspect of this embodiment, the straightening     is a cold straightening, in one embodiment, carried out at ambient     temperature, in one embodiment, at a temperature in the range from     about 10 to about 100° C., in one embodiment, in the range from     about 15 to about 80° C., in one embodiment, in the range from about     20 to about 50° C. -   |20| An alloy obtainable by a process according to any of the     embodiments |11| to |19|. -   |21| An electrical wire comprising an alloy according to any of the     embodiments |1| to |10| or |20|. -   |22| A medical device comprising a wire according to embodiment     |21|. -   |23| A pacemaker, an implantable cardioverter defibrillator, a     cardiac resynchronization device, a neuromodulation device, a     cochlea implant or any other implantable stimulation device     comprising a wire according to embodiment |21|.

Alloy

The Cr, Ni, Mo and Co alloy include two or more elements, in one embodiment, as a solid mixture, in one embodiment, with an enthalpy of mixing of the constituent elements of less than about 10 KJ/mol, in one embodiment, less than about 5 KJ/mol, in one embodiment, less than about 1 KJ/mol. The Cr, Ni, Mo and Co alloy include Cr, Ni, Mo and Co as major constituents, in one embodiment, with at least about 95 wt. %, in one embodiment, at least about 99 wt. %, further in one embodiment, at least about 99.9 wt. %, in one embodiment, at least about 99.95 wt. % of the alloy being Cr, Ni, Mo and Co.

A composition of the Cr, Ni, Mo and Co alloy improves favourable properties of the alloy, for example resistance to fatigue and/or corrosion resistance, in one embodiment, both.

In one embodiment the properties of the alloy to be improved by limiting the content of impurities or limiting the content of a combination of different impurities, in one embodiment, according the embodiments.

In one embodiment, there is a low, in one embodiment, zero concentration of inclusions in the alloy. This is in one embodiment, achieved by limiting the content of impurities. In one embodiment, the alloy contain less than about 0.01%, in one embodiment, less than about 0.005%, in one embodiment, less than about 0.001% inclusions. The % of inclusions is in one embodiment, determined using the microscopic inspection method given in the test methods. Content of inclusions as % is there determined as the proportion of the cross sectional area of the sample surface made up of inclusions. In some instances, the alloy includes a low, in one embodiment, a zero concentration of inorganic non-metallic solid inclusions, in one embodiment, of inorganic oxide inclusions. Inorganic oxides in this context can refer to metal oxides, non-metal oxides and metalloid-oxides. In some cases the alloy includes a low, in one embodiment, a zero concentration of inclusions comprising one or more selected from the group consisting of: Si, Al, Ti, Zr and B; in one embodiment, selected form the group consisting of: Si Ti, and Al.

In one embodiment, one or more treating material(s) is/are contacted with the mixture of the process in order to remove oxygen from the mixture of the process, in one embodiment, by incorporation of the oxygen into a dross and removal of the dross. Treating materials in this context include one or more selected from the list consisting of: Al, Mg, Ca and Ce; in one embodiment, in the form of an element and/or in the form of an alloy, wherein the alloy in one embodiment, contains a further metal being selected from group consisting of Cr, Ni, Mo and Co or at least two thereof, in one embodiment, Ni.

In order to achieve the concentrations of constituents of the alloy, described above in the embodiments, the skilled person may vary the proportions of starting materials employed in the preparation process. The proportions of the starting materials might not be equal to the proportions of constituents of the product, due to net loss or gain during the preparation process.

Process for Preparation of the Alloy

The process for the preparation of the alloy in one embodiment, includes the following steps:

-   -   a) A vacuum induction melting step;     -   b) A vacuum arc melting step.

In one embodiment, the process includes two or more vacuum induction melting steps. In another embodiment, the process includes two or more vacuum melting steps. In another embodiment, the process includes two or more vacuum induction melting steps and two or more vacuum arc melting steps.

In various embodiments, the process further includes one or more of the following steps:

-   -   c) An electro-slag melting step     -   d) A homogenization step     -   e) A cogging step     -   f) A finish roll step     -   g) A straightening step

In various embodiments, the process includes a combination of the above steps selected from the list consisting of: c), d), e), f), g), c)+d), c)+e), c)+f), c)+g), d)+e), d)+f), d)+g), e)+f), e)+g), f)+g), c)+d)+e), c)+d)+f), c)+d)+g), c)+e)+f), c)+e)+g), c)+f)+g), d)+e)+f), d)+e)+g), d)+f)+g), e)+f)+g), d)+e)+f)+g), c)+e)+f)+g), c)+d)+f)+g), c)+d)+e)+g), c)+d)+e)+f) and c)+d)+e)+f)+g).

In one embodiment, one or more of the steps c)-g) is carried out two or more times.

In vacuum induction melting steps, a material is heated by inducing an electric current in the material, in one embodiment, by electromagnetic induction. The pressure in the vacuum induction melting step is in one embodiment, below about 0.1 mbar, in one embodiment, below about 0.01 mbar, in one embodiment, below about 0.001 mbar. The vacuum induction melt step is in one embodiment, carried out in an oven, in one embodiment, with a low leak rate, in one embodiment, below about 0.1 mbar·l/s, in one embodiment, below about 0.01 mbar·l/s, in one embodiment, below about 0.001 mbar·l/s. The leak rate is in one embodiment, tested before the vacuum induction melting step by evacuating the oven, closing the valves of the oven, and measuring the rate of increase of pressure in the oven.

In one embodiment, the vacuum induction melting step is carried out in an inert atmosphere, in one embodiment, argon, in one embodiment, an atmosphere comprising at least about 90 wt. %, in one embodiment, at least about 99 wt. %, in one embodiment, at least about 99.9 wt. % of inert gas, in one embodiment, argon. In one aspect of this embodiment, the oven is evacuated and inert gas, in one embodiment, argon, introduced into the oven before melting. In one aspect of this embodiment, the pressure in the vacuum induction melting step is in the range from about 1 to about 200 mbar, in one embodiment, in the arrange from about 10 to about 150 mbar, in one embodiment, in the range from about 20 to about 100 mbar.

In vacuum arc melting steps, a material is heated by passing an electrical current through the material, in one embodiment, with an electrical power in the range from about 300 to about 1200 W/kg, in one embodiment, in the range from about 400 to about 1000 W/kg, in one embodiment, in the range from about 450 to about 900 W/kg, based on the mass of material heated. The pressure in the vacuum arc melting step is in one embodiment, below about 0.1 mbar, in one embodiment, below about 0.01 mbar, in one embodiment, below about 0.001 mbar. The vacuum arc melt step is in one embodiment, carried out in an oven, in one embodiment, with a low leak rate, in one embodiment, below about 0.1 mbar·l/s, in one embodiment, below about 0.05 mbar·l/s, in one embodiment, below about 0.01 mbar·l/s. The leak rate is in one embodiment, tested before the vacuum arc melting step by evacuating the oven, closing the valves of the oven, and measuring the rate of increase of pressure in the oven. In one embodiment, the vacuum arc melting step is carried out in an inert atmosphere, in one embodiment, argon, in one embodiment, an atmosphere comprising at least about 90 wt. %, in one embodiment, at least about 99 wt. %, in one embodiment, at least about 99.9 wt. % of inert gas, in one embodiment, argon. In one aspect of this embodiment, the oven is evacuated and inert gas, in one embodiment, argon, introduced into the oven before melting. In one aspect of this embodiment, the pressure in the vacuum arc melting step is in the range from about 0.001 to about 0.2 bar, in one embodiment, in the range from about 0.01 to about 0.15 bar, in one embodiment, in the range from about 0.05 to about 0.1 bar.

Homogenization steps according to one embodiment, allow reduction of inhomogeneity in a material, in one embodiment, by heating. In homogenization steps according one embodiment, a material is heated to a temperature which is below its melting temperature, in one embodiment, below its incipient melting temperature. In one embodiment, the material be homogenized for a duration in the range from about 10 min. to about 20 hours, in one embodiment, in the range from about 3 hours to about 10 hours, in one embodiment, in the range from about 5 hours to about 8 hours. Homogenization is in one embodiment, carried out in a vacuum or in a gaseous atmosphere, in one embodiment, in a gaseous atmosphere. In one embodiment, the homogenization step be carried out close to atmospheric pressure, in one embodiment, in the range from about 0.5 to about 1.5 bar, in one embodiment, in the range from about 0.8 to about 1.2 bar, in one embodiment, in the range from about 0.9 to about 1.1 bar. In one embodiment, the homogenization step is carried out in air.

In cogging steps according to one embodiment, the porosity or grain size or both of a material are reduced, in one embodiment, at elevated temperatures, in one embodiment, below the melting point of the material, in one embodiment, with the application of compressive force. Compressive forces may be applied locally or in a delocalised manner, in one embodiment, by one or more selected from the group consisting of: rolling, pressing, beating and turning. Where the material to be cogged has a mass below about 10 kg, in one embodiment, below about 8 kg, in one embodiment, below about 5 kg, rolling is done. Where the material to be cogged has a mass above about 10 kg, in one embodiment, above about 20 kg, in one embodiment, above about 30 kg, beating or turning is done. In one embodiment, the smallest dimension of the material is reduced during the cogging process.

Finish roll steps according to one embodiment reduce the smallest dimension of the material, in one embodiment, by passing the material through one or more pairs of rolls, in one embodiment, below the melting point of the material, in one embodiment, below its incipient melting point. In one embodiment, the finish roll step reduces the porosity or grain size of the material, in one embodiment, both.

Straightening in one embodiment, reduces the physical curvature of the material, in one embodiment, so as to facilitate further grinding or machining steps. Straightening is in one embodiment, carried out by applying compressive force. The straightening step is in one embodiment, carried out below the melting point of the material, in one embodiment, below its incipient melting point. In one embodiment, the process includes a hot straightening step. In one embodiment, the process includes a cold straightening step, in one embodiment, carried out at around ambient temperature. Cold straightening is in one embodiment, carried out at a temperature in the range from about 10 to about 100° C., in one embodiment, in the range from about 15 to about 80° C., in one embodiment, in the range from about 20 to about 50° C.

Leads, Wires and Medical Devices

In this text, reference is made variously to a coated or cladded wire, which includes a wire core and a shell. The shell might be coated or cladded onto the core wire.

A lead according to one embodiment includes at least one proximal connector, at least one distal electrode and a flexible elongated conductor that is electrically connecting the electrode(s) to the connector(s). In one embodiment, the elongated conductor is a coiled wire or a cable and includes the alloy.

A contribution to achieving at least one of the above mentioned objects is made by a wire comprising an alloy, in one embodiment, having a thickness in the range from about 10 to about 50 μm, in one embodiment, in the range from about 15 to about 35 μm. In one embodiment, the wire further includes silver metal.

In one embodiment, the lead includes a silver core and an alloy according to one embodiment, in one embodiment, present as a shell surrounding the silver core.

A contribution to achieving at least one of the above mentioned objects is made by a lead comprising one or more wires according to one embodiment, in one embodiment, grouped into two or more cables, each cable comprising two or more wires according to one embodiment. In one embodiment, the cables have a thickness in the range from about 0.05 to about 0.5 mm, in one embodiment, in the range from about 0.1 to 0.4 mm.

A contribution to achieving at least one of the above mentioned problems is made by a medical device, in one embodiment, a pacemaker, comprising a lead according to one embodiment. In one embodiment, a pacemaker includes:

-   -   An implantable pulse generator;     -   One or more leads according to one embodiment.

In one embodiment, the pacemaker includes one or more pulsers.

In one embodiment, the pacemaker includes one or more energy cells, in one embodiment, one or more electrical cells.

A process for the preparation of a wire includes the steps:

-   -   a) Providing a tube of alloy according to one embodiment;     -   b) At least partially filling the tube with Ag to obtain a         composite;     -   c) One or more drawing steps to reduce the diameter of the         composite;     -   d) Optionally one or more annealing steps to soften the         composite and facilitate drawing.

In one embodiment, the Ag content of the wire obtainable by the process is in the range from about 15 to about 50 wt. %, in one embodiment, in the range from about 17.5 to about 45.7 wt. %, in one embodiment, in the range from about 28.7 to about 37.7 wt. %, based on the total weight of the wire.

In one embodiment, the diameter of the wire obtainable by the process is in the range from about 5 to about 50 μm, in one embodiment, in the range from about 15 to about 35 μm.

In one embodiment, the filling degree of silver in the wire obtainable by the process is in the range from about 15% to about 41%, in one embodiment, in the range from about 20% to about 35%, in one embodiment, in the range from about 23% to about 33%.

It shall be understood that the method for manufacturing a composite wire, the composite wire manufactured by such method, and the medical device comprising such composite wire according to the independent claims have similar and/or identical embodiments, for example, as defined in the dependent claims. These and other aspects of the embodiments will become apparent from and be elucidated with reference to the embodiments described hereinafter.

FIG. 1 shows schematically a lead having a cable bundle 140, which includes cables 100. In this example, the cables 100 each include 7 wires 10. Each wire includes a first part or region 20 and a further, second part or region 30, wherein the first region 20 is interior to the region 30 along the length of the lead 140. The first region 20 is 41 area % of the cross sectional area the wire 10 and the further region is 59 area % of the cross sectional area of the wire 10, in each case based on the total cross sectional area of the wire 10. In this example, the first region 20 is silver. The further region 30 is a Cr, Ni, Mo and Co alloy as described above. In this example, the cable bundle 140 includes 7 cables 100, each cable 100 comprising 7 wires 10. The embodiments are not limited to this arrangement. For example, other arrangements of wires 10 in cables 100 and/or other arrangements of cable bundles 140 in leads are conceivable.

FIG. 2 shows schematically an apparatus for measuring fatigue resistance.

FIG. 3 shows schematically a pacemaker 50 with a pulse generator 70, and a lead 140 comprising an electrode 60. The lead 140 connects the pulse generator 70 and the heart tissue via the electrode 60.

FIG. 4 shows a cross sectional image of a wire of material according to example 2 (comparative) as observed by backscattered electron imaging according to the test method. A dark inclusion is indicated with an arrow.

FIG. 5 shows a cross sectional image of a wire of material according to example 2 (comparative) as observed by backscattered electron imaging according to the test method. FIG. 5 shows the same image as FIG. 4, but at higher magnification. A dark inclusion is indicated with the reference mark #A1.

FIG. 6 shows an analysis of elemental composition by energy dispersive x-ray spectroscopy according to the fracture surface analysis test method of the surface of an inclusion in a wire of material according to example 2 (comparative). The surface analysed is the inclusion indicated as #A1 in FIG. 5. For example, the analysis shows the presence of Al and Mg impurities and also of entities with a Cr—O bond.

FIG. 7 shows a cross sectional image of a wire of material according to example 2 (comparative) as observed by backscattered electron imaging according to the test method. A dark inclusion is indicated with the reference mark #A1.

FIG. 8 shows a cross sectional image of a wire of material according to example 2 (comparative) as observed by backscattered electron imaging according to the test method. The surface shown in FIG. 8 is taken from the same slice as that of FIG. 7.

FIG. 9 shows a cross sectional image of a wire of material according to example 2a (comparative) with an Ag core, as observed by backscattered electron imaging according to the test method. A dark inclusion is indicated with an arrow.

FIG. 10 shows a cross sectional image of a wire of material according to example 2a (comparative) with an Ag core, as observed by backscattered electron imaging according to the test method. FIG. 10 shows the same image as FIG. 9, but at higher magnification. A dark inclusion is indicated with the reference mark #A2.

FIG. 11 shows an analysis of elemental composition by energy dispersive x-ray spectroscopy according to the fracture surface analysis test method of the surface of an inclusion in a wire of material according to example 2a (comparative) with an Ag core. The surface analysed is the inclusion indicated as #A2 in FIG. 10. For example, the analysis shows the presence of Al impurities and also of entities with a Cr—O bond.

FIG. 12 shows a plot of fatigue results for a wire of material according to example 1 (inventive) and a wire of material according to example 2 (comparative). For example 1 (inventive), results are shown for 2 lots, lot A as represented by a solid circle and lot B as represented by a solid triangle. For example 2 (comparative), results are shown for 2 lots, lot C as represented by a hollow square and lot D as represented by a hollow diamond. The number of cycles before failure is shown as dependent on the stress amplitude applied in the test. Outliers, which performed poorly are indicated with arrows.

FIG. 13 shows a plot of fatigue results for a wire of material according to example 1a (inventive) with an Ag core and a wire of material according to example 2a (comparative) with an Ag core. For example 1a (inventive), results are shown for 3 lots, lot E as represented by a solid circle, lot F as represented by a solid triangle and lot G as represented by a solid square. For example 2a (comparative), results are shown for 3 lots, lot H as represented by a hollow square, lot J as represented by a hollow diamond and lot K as represented by a cross. The number of cycles before failure is shown as dependent on the stress amplitude applied in the test. Outliers, which performed poorly are indicated with arrows.

FIG. 14 shows a method for manufacturing a composite wire 10. The method for manufacturing the composite wire 10 includes the following steps:

In step S1, providing a first part 20 in form of a rod,

which means here preparing a rod made of a metal or alloy for the inner volume of the composite wire 10. Examples for the metal or alloy include Silver, Tantalum, Platinum, Gold, Copper or alloys thereof. The manufacturing includes a machining out of stock material. More specifically, the first part 20 is here a rod made of commercially pure silver with a diameter of 36 mm±0.25 mm and a length of 310 mm±2 mm. The maximum allowed straightness over the entire length of the rod is here 0.5 mm.

In step S2, providing a second part 30 in form of a tube surrounding the rod at least partially to form a rod-tube assembly,

which means here preparing a tube of a different metal or alloy for the outer volume of the composite wire 10. The manufacturing includes machining and drilling out of stock material. More specifically, the second part 30 is here a tube made of the Cr, Ni, Mo and Co alloy (fully annealed) with an inner diameter of 51 mm±0.25 mm, an outer diameter of 80 mm±0.25 mm and a length of 300 mm. The maximum allowed straightness over the entire length of the tube is here 0.5 mm for the inner diameter and the outer diameter of the tube, respectively. The specific dimensions mentioned above for the Silver rod and the Cr, Ni, Mo and Co alloy tube equals for a filling ratio of the Silver core of 25 percent.

In step S3, providing a clad part 40 in form of a cylinder surrounding the rod-tube assembly at least partially to form a cladded rod-tube assembly,

which means here preparing a container for the above mentioned assembly of rod and tube that includes of a metal or alloy with a in one embodiment, low friction during extrusion. The container is here made from sheet metal stock and includes a disc for a bottom and an elongated sheet for a mandrel. More specifically, the clad part 40 is here made out of commercially pure copper (fully annealed) with a sheet thickness of 1 mm. The disc diameter is 83 mm. The dimensions for the mandrel are 259 mm±0.1 mm in width and 380 mm±0.5 mm in length. The disc and the sheet are welded together so that they form a cylinder with one end open. Further, the rod and tube assembly are placed vertically into the container and an excess sheet material is round hammered onto a plug connected to a vacuum pump. A sealing agent may be used between the plug and sheet material for vacuum sealing, if needed. The assembly may be pre-heated to 150° C. and a vacuum of 10⁻² mbar may be applied for 2 hours. Finally, a top end of the copper sheet may be clamped between plug and assembly with suitable pliers, while the vacuum is still applied to maintain vacuum. The plug is then cut off from the assembly.

In step S4, extruding the cladded rod-tube assembly to form the composite wire 10, which means here using an extrusion machine for a deformation of the materials at a speed of 0.1-2 m/min (measured at an incoming diameter). The incoming diameter of an extrusion tool is here 90 mm for the above mentioned example, a reduction angle is here in a range of 10-40°, more specifically 20°. An outgoing diameter of the extrusion tool is here 20 mm, which equals an extrusion ratio of approximately 16. This may further include a pre-heating of the assembly at 900° C. for 2 hours before extrusion in e.g. an inert atmosphere.

In step S5, further deforming the composite wire 10 by wire drawing. For a reduction from 20 mm to 5 mm diameter, a following drawing die sequence is here used, that equals to an elongation per pass of 16%.

DV in % 16.00 Inlet diameter Die diameter in mm in mm 1 18.5695 2 17.2414 3 16.0082 4 14.8633 5 13.8002 6 12.8132 7 11.8967 8 11.0458 9 10.2558 10 9.5223 11 8.8412 12 8.2088 13 7.6217 14 7.0766 15 6.5704

In step S6, deforming the composite wire 10 into a composite wire coil. This can also be done after extrusion.

In step S7, placing the composite wire coil in nitric acid to etch off the copper clad that was used as an agent for deformation. The copper clad used to reduce friction during extrusion is here etched-off by e.g. nitric acid on the straight bar after extrusion or, alternatively, the copper clad can be etched-off at a later point of time, but before an annealing of the composite wire 10.

In step S8, annealing the composite wire 10 in its coil shape.

Test Methods Alloy Composition

For a quantitative chemical analysis of the alloy, the following methods are used:

-   -   a) the main components of the alloy (Co, Cr, Ni, Mo) are         measured by X-ray fluorescence XRF using the XRF Lab Report—S8         TIGER from the company BRUKER (Bruker AXS GmbH Östliche         Rheinbrückenstr. 49, 76187 Karlsruhe, Germany)     -   b) Trace elements present in the alloy (Mn, P, Si, Fe, Ti, Al,         B, Mg, Ca, Ce, Ti) are measured by glow discharge mass         spectrometry (GDMS) using the ASTRUM from Nu Instruments (Nu         Instruments Limited, Unit 74, Clywedog Road South, Wrexham, LL13         9XS UK.)     -   c) Gas or non-metallic components in the alloy (H, O, C, N, S)         are measured by carrier-gas hot extraction using the ONH836 from         LECO (LECO Corporation, 3000 Lakeview Avenue, St. Joseph, Mich.         49085)

Leak Rate

The leak rate of the furnace chamber is measured using the following procedure:

The Vacuum furnace chamber is evacuated to the required pressure by a vacuum pumping station. When the required pressure is reached, the pressure valve between the vacuum furnace chamber and the vacuum pumping station is closed. The pressure increase of the vacuum furnace chamber over a given length of time defines the leak rate of the equipment.

Fatigue Resistance

Rotating beam fatigue testing was carried out using Valley Instruments model #100 test machine (FIG. 2) according to Valley Instruments Wire Fatigue Tester Model #100 user manual (Valley Instruments (Division of Positool Technologies, Inc.), Brunswick, Ohio, USA. Fatigue Tester Model 100 Manual). The equipment consists of a synchronous motor rotating at 3600 rpm. For each test of a wire specimen, a sample having a predefined length is fixed in a custom fine-wire collet at one end, looped through a complete 180 degree turn and is placed at the other end in a low-friction bushing in which it is free to rotate. The synchronous motor of the test device is directly clocked by a counter where the number of cycles is shown in a LCD-display. The fatigue testers are equipped with a sensor to detect the wire fracture which automatically stops the timer, means the display of the timer shows the number of cycles until failure. If no fracture occurs within 100 Million cycles, the test is stopped.

Valley Instruments Wire Fatigue Tester Model #100 user manual (Valley Instruments (Division of Positool Technologies, Inc.), Brunswick, Ohio, USA. Fatigue Tester Model 100 Manual) describes that a loop, formed by an elastic length held so that the axes of the specimen at the point of retention are exactly parallel, assumes a shape in which:

-   -   (1) The length of the loop is 2.19 times the base,     -   (2) The height of the arch is always 0.835 times the base,     -   (3) The minimum radius of the curvature occurs at the apex of         the arch and is exactly 0.417 times the base, and     -   (4) The bending stress at the point of minimum curvature bears a         simple reciprocal linear relationship to any of the four         physical dimensions (length, height, base, and minimum         curvature).

The following formulas express the exact relationship:

C=1.198*E*d/S

h=0.835*C

L=2.19*C

R=0.417*C

P=0.141*E*d ⁴ /C ²

Nomenclature:

-   -   C=chuck to bushing distance     -   d=diameter of wire     -   h=height of loop     -   E=modulus of elasticity     -   L=length of wire external to chucks     -   R=minimum of radius of curvature     -   S=bending stress     -   P=bushing load or lateral force at the chuck

With the above listed formula, the bending stress S (at the peak of the loop) can be calculated by the following equation:

S=1.198*E*d/C

The machine set-up involves calculating the desired sample length and center distance using the modulus of elasticity of the material and equations developed by Valley Instruments Company (user manual).

Microscopic Inspection Method for Micro-Cleanliness

Definition: Inclusions are defined as internal flaws or contaminations (such as nitrides or oxides) within the billet or rod from which the wire or tube is produced. The transverse inclusion size is defined as the largest dimension of an internal flaw measured on transverse cross-sections of the billet, rod or wire. The longitudinal inclusion size is defined as the largest dimension of an internal flaw measured on longitudinal cross-sections of the billet, rod or wire. A cross-section diametral line is defined as any line within the cross-section having a length equal to or greater than 95% of the true cross-section diameter.

General Test Procedure:

a) Sectioning

-   -   For each material lot, the billet, rod or wire is to be         sectioned at each end so that there are an equal number of cross         sections sampled at the one end as there are samples at the         other end (number of samples taken from each end shall differ by         no more than one). The total number of cross sections samples         depends on the diameter of the billet, rod or wire and is         specified in Table 1. The length of each cross section is to be         less than its diameter.

b) Imaging

-   -   For each billet, rod or solid wire cross-section,         non-overlapping images are to be taken at 500× magnification         along diametral lines so that the total examined area per sample         is at least 1.77 mm². A cross-section diametral line is defined         as any line within the cross-section having a length equal to or         greater than 95% of the true cross-section diameter. Angular         separation between two diametral lines on a cross-section shall         be a minimum of 60 degrees. The number of images and the number         of diametral lines depends on the diameter of the billet, rod or         wire and is specified in Table 1. The total number of images is         shown in Table 1 and was calculated based on the number of         images per sample and the number of samples.

c) Measurement

-   -   Each of the images is to be inspected to detect the presence of         inclusions or strings of inclusions that exceed a size of 3.0 μm         in their largest dimension. The image inspection may be         accomplished either by manual examination or by automated         scanning.

TABLE 1 cross section diameter of billet, rod or Number of wire diametral equal lines per Number to or but no section (no of greater greater requirement images Number of Total images than than for tube per cross-sections per lot [mm] [mm] samples) section transverse longitudinal transverse longitudinal 2.54 3.80 5 40 12 12 480 480 3.81 5.71 3 40 12 12 480 480 5.72 11.42 2 40 12 12 480 480 11.43 13.96 1 40 12 12 480 480 13.97 17.14 1 48 10 10 480 480 17.15 21.58 1 60 8 8 480 480 21.59 27.93 1 80 6 6 480 480 27.94 33.01 1 96 5 5 480 480 33.02 43.17 1 120 4 4 480 480 43.18 57.14 1 160 3 3 480 480

Fracture Surface Analysis of Wire Samples

The test method to analyse fracture surfaces of fatigue tested samples was Scanning electron microscopy (SEM). A Zeiss Ultra 55 Gemini was used for the sample analysis of the one embodiment and comparative samples.

Two imaging modes were used to analyse and illustrate the tested samples.

-   -   a) SE: the detection of secondary electrons (SE) results in         images with a well-defined, three-dimensional appearance. The         surface topography can be illustrated in high resolution. FIGS.         5, 7, 8 and 10 are secondary electron images.     -   b) BSE: backscatter electrons (BSE) are used to detect contrast         between areas with different chemical compositions. Heavy         elements (high atomic number) backscatter electrons more         strongly than light elements (low atomic number), and thus         appear brighter in the image. FIGS. 4 and 9 are BSE images.

Energy-dispersive X-ray spectroscopy (EDS, EDX) was used for the elemental analysis of features (inclusions/particles) found on the fatigue resistance test samples. A high-energy beam of electrons is focused onto the location of the sample being analysed. This leads to the emission of characteristic X-rays which allows the elemental composition of the feature (inclusions/particles) to be measured. FIGS. 6 and 11 show EDX scans.

EXAMPLES

The MP35N heats were VIM-VAR melted, to minimize the impurity content and to obtain a sound ingot with good chemical uniformity and metallurgical properties. The chemistry of representative heats: Heat 1, Heat 2 and Heat 3 are listed in Table 3. The table also provides the chemistry of a VIM-VAR melted, commercially available MP35N alloy and for reference the chemical requirements per ASTM F562-13, a standard specification for wrought MP35N alloy. The major constituents of MP35N alloy are Co, Ni, Cr and Mo. The new alloy heats were melted in 2 steps. The first melting step was Vacuum Induction Melting (VIM). The VIM furnace consists of a water cooled vacuum melt chamber, an oxide ceramic crucible held in a cylindrical induction heating coil inside the melt chamber, an AC electric power supply, a vacuum pumping system, a raw material adding chamber and a cylindrical metal mold held below and offset from the crucible-induction coil assembly. The vacuum melt chamber, raw material adding chamber and vacuum pumping system are separated by isolation valves. The induction heating coil is water cooled. Electric current from the power supply passes through the induction heating coil creating a magnetic field inside the furnace. The magnetic field induces eddy currents inside the raw materials causing Joule heating. Joule heating raises the temperature of the raw materials to above their melting point. The magnetic field mixes the liquid raw materials to make a homogeneous alloy. The crucible is tilted to pour the liquid alloy from the crucible into the mold. The alloy cools to a solid in the mold under vacuum and is removed from the furnace. The alloy ingot is removed from the mold and it is prepared for re-melting.

For the example heats, 136 kilograms of elemental raw materials were placed in the furnace in proportions calculated to make the aim chemistry. The VIM furnace was closed and pumped down to □ 0.00001 bar. A leak-up rate was measured after reaching the desired vacuum pressure level to ensure a vacuum tight furnace. The leak-up rate was □ 0.00001 bar/min. Electric power was applied to the induction heating coil. Once the melt was in progress, the vacuum level was recorded at specified intervals to monitor the progress of melting and the mixing and reaction of all of the raw materials. When the reactions ceased as indicated by a constant vacuum pressure level, the heat was poured into a 152.4 mm diameter cylindrical mold.

Each heat was subsequently re-melted by a Vacuum Arc Re-melting (VAR) process to make a 203.2 mm diameter ingot. The VAR furnace consists of water cooled vacuum chamber, a 203.2 mm diameter water cooled copper crucible, a direct current electric power supply, a vacuum pumping system, isolation valves and a computer based electrical system to monitor and control the application of current to the electrode inside the vacuum chamber. The furnace was pumped down to □ 0.000006 bar before carrying out the leak-up rate test. A leak rate of □ 0.000006 bar/min was obtained. The electrode was moved to a close proximity to the bottom of the crucible. Electric power was applied at a level to cause an electric arc to be struck between the crucible bottom and the alloy electrode. The electric arc causes the electrode to melt and drip into the bottom of the crucible creating a liquid metal pool that solidifies as the arc moves away from the molten pool. The process was continued at a controlled rate until the electrode was consumed. The power was turned off and the ingot was cooled under vacuum. The ingot was removed from the furnace for processing to product.

The as-cast ingot was charged into a gas-fired front opening box furnace with ambient air atmosphere. The furnace was preset to a temperature of 815° C. Upon equilibration of furnace temperature, the ingot was held for additional 4 hours prior to raising the furnace temperature. The ingot was then heated to 1177° C. at a heating rate of 200 K per hour. The ingot was held for 7 hours at 1177° C. for homogenization. After homogenization, the ingot was hot rolled from 203 mm to 137 mm round cornered square (RCS) billet using a 559 mm diameter Morgenshammer Mill operating at ambient temperature. The Morgenshammer Mill is a manually operated tilt table mill with 3 high rolls allowing heavy bar to be rolled alternately between the bottom and middle roll and the top and middle roll. After hot rolling the RCS billet was air cooled, abrasively ground by hand to remove surface imperfections and cut to square the ends. The billet was reheated and hot rolled to 51 mm RCS at 1177° C. on the 559 mm Morgenshammer Mill. The RCS was cut to shorter lengths of final rolling on a hand operated 406 mm diameter Morgenshammer Mill with 3 high rolls. All bar manipulation on this mill is done by hand at floor level. The RCS was reheated at 1177° C. and rolled to 33.4 mm round bars and air cooled to ambient temperature. The rolled bars were then reheated to 1038° C. and held for 30 minutes for hot rotary straightening. After straightening, the bars were air cooled to room temperature. The bars were rough centerless ground, ultrasonic tested for voids and then centerless ground to final size.

For manufacturing of clad-wires, the grinded bars were gun-drilled to produce hollows for subsequent tube drawing. Tubes were filled with Ag-rods and cold-drawn using diamond dies and mineral oil. For a final wire diameter of 127 μm, the last intermediate annealing was carried out at a wire diameter of 157.5 μm at 900-950° C. in Argon atmosphere. From the last intermediate annealing until the final diameter of the wire, 35% cold-work were applied. Three wire lots were manufactured having UTS values of 1456, 1469 and 1474 MPa. For bare wire, the bars were further hot-rolled to 0.2 inch outer diameter followed by cold-drawing. For 102 μm final size wire, the last intermediate annealing was carried out at a wire diameter of 122 μm at 1100° C. in Argon atmosphere to apply 30% cold-work to the final size. Two wire lots were manufactured having UTS values of 1870 and 1875 MPa. The wires of inventive example 1 (Lots A & B) and the cladded wires of inventive example 1a (Lots E, F & G) were made using the alloy of Heat 1 in table 3. The wires of comparative example 2 (lots C & D) and the cladded wires of comparative example 2a (lots H, J & K) were made from the alloy of the commercial heat in table 3 obtained from Fort Wayne Metals, Inc., USA under the trade name 35 NLT®.

TABLE 2 Material Example 1 Example 1a with (inventive) 28% Ag (inventive) Batch Lot A Lot B Lot E Lot F Lot G UTS [MPa] 1870 1875 1456 1469 1474 YM [GPa] 190 191 121 121 122 Elongation 2.8 2.9 2.2 2.3 2.3 [%]

The processed alloy was also obtainable from SAES Smart Materials, Inc. Alloys for the further examples were acquired from SAES Smart Materials, Inc.

TABLE 3 Commercial ASTM Heat 1 Heat 2 Heat 3 Heat F-562-13 Element Wt. % Wt. % Wt. % Wt. % Wt. % C 0.0039 0.0091 0.0106 0.005 <0.0250 B 0.000065 0.000067 0.000008 0.01 <0.015 P 0.00018 0.000095 0.000056 0.001 <0.015 S 0.00056 0.00026 0.00036 0.001 <0.010 Mn 0.00028 0.00021 0.00013 0.017 <0.15 Si 0.0042 0.0053 0.0061 0.034 <0.15 Al 0.00023 0.00054 0.00043 0.023 NA Mg <0.000001 0.000003 0.000005 0.001 NA Ca <0.000005 <0.000005 <0.000005 NA NA Ce <0.000001 <0.000001 <0.000001 NA NA Fe 0.021 0.023 0.023 0.08 <1 Ti 0.00017 0.000038 0.000023 0.001 <1 O 0.0085 0.0056 0.0035 0.0021 NA N 0.0022 0.0009 0.0007 0.0022 NA Cr 19.6 19.7 20 20.62 19-21 Ni 35.7 34.8 34.9 34.91 33-37 Mo 10 9.93 9.7 9.47   9-10.5 Co balance balance balance balance balance

Microscopic Inspection for Microcleanliness of the Alloy

The microscopic inspection for microcleanliness of the inventive alloy (example 1 and example 1a with an Ag core) and of the comparative alloy (example 2 and example 2a with an Ag core) was carried out according to the procedure and test method described above. Of 4 rods with an outer diameter of 31.75 mm, 5 transverse and 5 longitudinal sections were taken according to table 1 and metallographically prepared. The sections included a continuous plane from two surface locations and through the approximated center of the bar. The metallographically prepared sections were examined in the as-polished condition by scanning electron microscopy (SEM) using backscattered electron imaging (BEI). In BEI, the brightness of sample features is proportional to the atomic weight of the elements constituting those features. Thus, in BEI, present inclusions consisting of heavier elements than the surrounding matrix material appear brighter than the matrix material. Inclusions consisting of lighter elements than the surrounding matrix material appear darker than the matrix material. Since nonmetallic inclusions (e.g. oxide or nitride inclusions) consist of lighter elements than the alloys of example 1 and example 2, in BEI these ceramic inclusions appear darker than the surrounding matrix material. Images were acquired at a magnification of 500× along a diametral line extending across the entire bar. Analysis of features darker and brighter than the background was conducted on the images using image analysis software to determine the maximum dimension for each detected feature. The largest dimension and area were recorded for each individual feature. The inclusions were categorized by largest dimension into 1 □m groups up to 14 □m. The total area of the dark and bright features was also calculated. Inclusions greater than 14 □m were also counted. Features smaller than 3.0 □m were not included in the measurements.

For each section, forty-eight fields of view were evaluated. For each direction, longitudinal and transverse, 480 images with a total area of 22.6 mm² were evaluated. The samples contained features that appeared darker and brighter than the bulk material using backscattered electron imaging. The darker features have a lower mean atomic number than the background and the brighter features have a higher mean atomic number than the background.

Results of the inclusion analysis of example 1 are shown in tables 4-6. Results of the inclusion analysis of example 2 are shown in tables 7-10. Image fields showing typical dark (ceramic) inclusions are shown in FIGS. 4, 5, 7-10.

Alloy of One Embodiment (Example 1)

TABLE 4 FEATURE COUNT TOTALS/EXAMPLE 1 Largest Number of Features Dimension Longitudinal Transverse [□m] Dark Bright Dark Bright 3.0-3.9 15 0 14 0 4.0-4.9 4 0 2 0 5.0-5.9 2 0 1 0 6.0-6.9 0 0 0 0 7.0-7.9 0 0 0 0 8.0-8.9 0 0 0 0 9.0-9.9 0 0 0 0 10.0-10.9 0 0 0 0 11.0-11.9 0 0 0 0 12.0-12.9 0 0 0 0 13.0-13.9 0 0 0 0 14.0-14.9 0 0 0 0 >14.9 0 0 0 0 Total 21 0 17 0

TABLE 5 TOTAL INCLUSION AREA MEASUREMENTS FOR EXAMPLE 1 Area of Inclusions >3 μm in Length for Examination Region Darker Brighter All Percent Percent Percent of of of Total Total Total Total Area Total Area Total Area Sample [□ m²] [%] [□ m²] [%] [□ m²] [%] Longitudinal 121 0.0006 0 0.0000 121 0.0006 Transverse  97 0.0005 0 0.0000  97 0.0005

TABLE 6 LONGEST DARK FEATURES FOR EXAMPLE 1 Feature Dimensions, [μm] Number Length Breadth Direction 1 5.6 3.0 Longitudinal 2 5.4 3.7 Longitudinal 3 5.4 2.9 Longitudinal 4 4.9 2.2 Longitudinal 5 4.7 3.6 Longitudinal 6 4.6 1.9 Longitudinal 7 4.5 2.7 Longitudinal 8 4.5 2.4 Longitudinal 9 4.1 2.4 Longitudinal 10 3.9 3.0 Longitudinal

Example 2 (Comparative)

TABLE 7 FEATURE COUNT TOTALS/BARS 1-10/ALL SAMPLES Largest Number of Features Dimension Longitudinal Transverse [□m] Dark Bright Dark Bright 3.0-3.9 25 21 6 46 4.0-4.9 19 7 3 11 5.0-5.9 7 1 1 1 6.0-6.9 6 — — 1 7.0-7.9 7 — — — 8.0-8.9 4 — — — 9.0-9.9 1 — — — 10.0-10.9 2 — — — 11.0-11.9 2 — — — 12.0-12.9 — — — — 13.0-13.9 — — — — 14.0-14.9 — — — — >14.9 4 — — — Total 77 29 10 59

TABLE 8 TOTAL INCLUSION AREA MEASUREMENTS FOR EXAMPLE 2 Area of Inclusions >3 μm in Length for Examination Region Darker Brighter All Percent Percent Percent of of of Total Total Total Total Area Total Area Total Area Sample [□ m²] [%] [□ m²] [%] [□ m²] [%] Longitudinal 409  0.0018  75  0.0003  484  0.0021 Transverse 169 10.0003 1152 10.0007 1221 10.0010

TABLE 9 LONGEST DARK FEATURES FOR EXAMPLE 2 Feature Dimensions, [μm] Number Length Breadth Direction 1 33.4 1.9 Longitudinal 2 18.9 1.6 Longitudinal 3 17.8 2.3 Longitudinal 4 15.4 1.4 Longitudinal 5 11.8 1.0 Longitudinal 6 11.1 1.1 Longitudinal 7 10.6 1.0 Longitudinal 8 10.3 1.8 Longitudinal 9 9.5 1.5 Longitudinal 10 8.9 2.2 Longitudinal

TABLE 10 LONGEST BRIGHT FEATURES FOR EXAMPLE 2 Feature Dimensions, [μm] Number Length Breadth Direction 1 6.0 1.6 Transverse 2 5.6 2.8 Longitudinal 3 5.1 1.8 Transverse 4 4.9 2.3 Transverse 5 1.9 1.8 Transverse 6 1.0 1.8 Longitudinal 7 4.6 1.3 Transverse 8 4.5 1.2 Transverse 9 4.4 1.6 Longitudinal 10 4.4 0.9 Transverse

According to Table 8 of example 2 (comparative), the total area of dark inclusions found is 478 μm² (409 μm² in longitudinal direction and 69 μm² in transverse direction). According to Table 5 of example 1 (inventive), the total area of dark inclusions found is only 218 μm² (121 μm² in longitudinal direction and 97 μm² in transverse direction). So the amount of dark inclusions (Percent of total area) in example 1 (inventive) is only 4.8 ppm (0.00048%) while in example 2 (comparative) the amount of dark inclusions is 11 ppm (0.0011%). In terms of inclusions (micro-cleanliness) this means that example 1 (inventive) is more than 2 times cleaner than example 2 (comparative).

Fatigue Test Results

Two lots of wire of example 1 (dia. 102 μm) were tested against two lots of wire or example 2 (same diameter—102 μm) having comparable mechanical properties (UTS of 1862-1875 MPa).

TABLE 11 Material Example 1 (inventive) Example 2 (comparative) Batch Lot A Lot B Lot C (FIG. 5 & 6) Lot D UTS [MPa] 1870 1875 1862 1871 YM [GPa] 190 191 190 190 Elongation 2.8 2.9 2.7 2.8 [%]

At an applied stress of 700 MPa, the wire of all four lots reached the fatigue endurance limit, means the wire does not fail and tests are stopped after 100 Million cycles. While the wire of example 1 showed no outliers at 700 MPa and below, 4 samples of example 2 failed at less than 2.7 Million cycles and two other samples ran 40-50 Million cycles. All other samples tested at an applied stress of 700 MPa and below survived 100 Million cycles without rupture. For Example 2 wire lot C, sample C25 tested at an applied stress of 700 MPa broke after only 71,790 cycles and sample C31 tested at an applied stress of 520 MPa broke after only 145,260 cycles. Sample C26 tested at an applied stress of 700 MPa broke after 47,547,540 cycles and sample C29 tested at an applied stress of 700 MPa broke after 41,282,990 cycles. For example 2 wire lot D, sample D27 tested at an applied stress of 700 MPa broke after only 549,227 cycles and sample D35 tested at an applied stress of 520 MPa broke after only 2,689,952 cycles.

SEM-images of sample C25 shows an inclusion at the fracture surface. In EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. This mixed-oxide inclusion was identified as the crack initiation point for the early failure of this sample. An SEM-image of sample D35 also shows an inclusion at the fracture surface. Again, in EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. Also this mixed-oxide inclusion can be identified as the crack initiation point for the early failure of this sample. SEM investigations of samples C31 and D27 also showed oxide-inclusions at the fracture surface which were identified causing the early failure. For both samples, the same elements (Aluminium, Magnesium, Chromium, Oxygen) show high peaks in EDX analysis for these two samples.

TABLE 12 Example 1 Example 1 Example 2 Example 2 stress (inventive) (inventive) (Lot (comparative) (comparative) level (Lot A) B) (Lot C) (Lot D) [MPa] No. of cycles No. of cycles No. of cycles No. of cycles 1430 21092 66720 20700 35130 1430 12740 63781 22140 57120 1430 28919 59140 36120 32460 1430 19334 37942 23550 35010 1430 18119 39178 18270 28996 1430 21983 22380 18150 33313 1040 38670 128644 136680 149971 1040 58474 218106 1004289 308580 1040 46980 194108 8656363 80766 1040 34806 41310 107640 178770 1040 38045 539089 7856526 74323 1040 39120 290101 6852041 127650 880 5888420 4715690 39485962 72523366 880 4233055 5816670 102020453 100000000 880 6324748 2144125 100800000 6171230 880 13571905 2068519 114000000 4407264 880 8824316 1725656 101000000 102000000 880 7680042 1815390 100000000 57462763 800 104700000 40051186 — — 800 96874223 16938278 — — 800 59716187 26518613 — — 800 54411683 79084889 — — 800 64971417 46467823 — — 800 100000000 24231864 — — 700 103000000 105000000 71790 100000000 700 109852488 97119288 47547540 100000000 700 101589761 107000000 100000000 549227 700 101623566 104000000 100000000 101337563 700 102000000 101000000 41282990 100000000 700 103000000 103000000 100000000 100000000 520 100000000 100000000 145260 100000000 520 118987000 106000000 110800000 110800000 520 102064330 102000000 101000000 101000000 520 100963860 100613526 100500000 100500000 520 100845911 100845911 108000000 2689952 520 101009712 101006089 100000000 112000000

These fatigue test results are plotted in FIG. 12. As can be seen from this plot, lots C and D (comparative) show significantly more undesired outliers that for lots A and B (inventive).

Three lots of example 1a/Ag28% wire (diameter 127 μm) were also tested against three lots of example 2a wire (same diameter—127 μm). All six wire lots have comparable mechanical properties (UTS of 1456-1475 MPa).

TABLE 13 Example 2a + 28 wt. % Ag (comparative) Example 1a + 28 wt. % Ag Lot J — (inventive) (FIG. Batch Lot E Lot F Lot G Lot H 10 & 11) Lot K UTS [MPa] 1456 1469 1474 1460 1462 1475 YM [GPa] 121 121 122 121 122 122 Elongation 2.2 2.3 2.3 2.1 2.0 2.3 [%]

At an applied stress of 414 MPa, the wire of all four lots reached the fatigue endurance limit, means the wire does not fail and tests are stopped after 100 Million cycles. While example 1a/Ag28% wire showed no outliers at 414 MPa and below, 4 samples of example 2a/Ag28% wire failed at less than 1.4 Million cycles. All other samples tested at an applied stress of 414 MPa and below survived 100 Million cycles without rupture. For example 2a/Ag28% wire lot H, sample H24 tested at an applied stress of 414 MPa broke after only 1,041,679 cycles. Sample J18 tested at an applied stress of 518 MPa broke after 588,028 cycles and sample J23 tested at an applied stress of 414 MPa broke after 263,488 cycles. Sample K24 tested at an applied stress of 414 MPa broke after 1,355,189 cycles. As an example, SEM-images of sample J23 show an inclusion at the fracture surface. In EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. This mixed-oxide inclusion was identified as the crack initiation point for the early failure of this sample. SEM investigations of samples H24, J18 and K24 also showed oxide-inclusions at the fracture surface which were identified causing the early failure. For all three samples, the same elements (Aluminium, Magnesium, Chromium, Oxygen) show high peaks in EDX analysis for these three samples.

TABLE 14 Example 1a + 28 wt. % Ag Example 2a + 28 wt. % Ag stress lot E lot F lot G lot H lot J lot K level No. of No. of No. of No. of No. of No. of [MPa] cycles cycles cycles cycles cycles cycles 969 31,887 33,065 21,487 47,982 38,148 32,926 969 29,321 28,116 23,461 43,661 41,085 20,818 969 32,555 29,941 28,763 30,298 33,187 32,299 969 26,918 23,418 18,464 37,888 36,247 38,901 969 22,089 30,467 20,198 43,092 41,944 42,978 725 246,766 231,412 114,746 74,414 235,494 109,597 725 199,054 189,441 123,746 79,498 128,377 92,419 725 287,665 262,994 168,374 94,638 118,922 91,877 725 200,822 186,242 145,355 75,062 162,522 102,834 725 500,045 290,377 169,176 62,082 238,611 99,864 580 1,405,296 1,612,743 979,651 409,644 6,780,968 311,974 580 1,077,510 1,131,168 1,846,396 668,132 12,545,505 8,369,715 580 8,201,513 993,416 1,684,673 1,031,447 1,945,002 3,001,478 580 2,511,763 2,197,173 639,464 342,282 2,639,912 219,634 580 841,436 884,196 2,076,465 3,539,353 8,566,249 2,009,899 518 40,051,186 86,414,732 71,763,385 100,000,000 100,000,000 100,000,000 518 100,000,000 78,411,674 83,944,821 100,000,000 100,000,000 100,000,000 518 79,084,889 100,000,000 35,946,337 100,000,000 588,028 100,000,000 518 46,467,823 100,000,000 100,000,000 100,000,000 100,000,000 100,000,000 518 100,000,000 87,867,423 54,676,179 100,000,000 100,000,000 100,000,000 414 100,000,000 100,000,000 100,000,000 100,000,000 100,000,000 100,000,000 414 100,000,000 100,000,000 100,000,000 100,000,000 100,000,000 100,000,000 414 100,000,000 100,000,000 98,674,345 100,000,000 263,488 100,000,000 414 100,000,000 100,000,000 100,000,000 1,041,679 100,000,000 1,355,189 414 100,000,000 100,000,000 96,674,523 100,000,000 100,000,000 100,000,000 329 100,000,000 100,000,000 100,000,000 — — — 329 100,000,000 100,000,000 100,000,000 — — — 329 100,000,000 100,000,000 100,000,000 — — — 329 100,000,000 100,000,000 100,000,000 — — — 329 100,000,000 100,000,000 100,000,000 — — — These fatigue test results are plotted in FIG. 13. As can be seen from this plot, lots H, J and K (comparative) show significantly more undesired outliers that for lots E, F and G (inventive).

Pacemaker Lead

A wire with thickness 25 μm was prepared according to the method described above and with compositions of the alloy as given in table 3. The wires were arranged into a lead as described in FIG. 1. The leads were tested for fatigue resistance and for impurity inclusions. The results are shown in table 15.

TABLE 15 Example Fatigue resistance Purity from inclusions Heat 1 ++ ++ Heat 2 ++ ++ Heat 3 ++ ++ Commercial heat − − ++ = very good, − = poor

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present embodiments. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that embodiments be limited only by the claims and the equivalents thereof. 

What is claimed is:
 1. A method for manufacturing a composite wire comprising: providing a first part in form of a rod, providing a second part in form of a tube surrounding the rod at least partially to form a rod-tube assembly, providing a clad part in form of a cylinder surrounding the rod-tube assembly at least partially to form a cladded rod-tube assembly, extruding the cladded rod-tube assembly to form the composite wire wherein the first part or the second part comprises an alloy comprising the following alloy components: a) Cr in the range from about 10 to about 30 wt. %; b) Ni in the range from about 20 to about 50 wt. %; c) Mo in the range from about 2 to about 20 wt. %; d) Co in the range from about 10 to about 50 wt. %; wherein the Al content of the alloy is less than about 0.01 wt. %; wherein each wt. % is based on the total weight of the alloy.
 2. The method according to claim 1, wherein the Cr, Ni, Mo and Co components are major constituents of the first part or the second part with at least about 95 wt. % of the alloy being Cr, Ni, Mo and Co.
 3. The method according to claim 1, wherein the second part comprises the Cr, Ni, Mo and Co alloy.
 4. The method according to claim 1, wherein the first part comprises a metallic material.
 5. The method according to claim 1, wherein the first part comprises at least one of a group of Silver, Platinum, Tantalum, Gold, Copper and alloys thereof.
 6. The method according to claim 1, wherein the clad part comprises a material with a lower friction coefficient than the second part.
 7. The method according to claim 1, further comprising a heating of the cladded rod-tube assembly before the extrusion step.
 8. The method according to claim 1, further comprising an applying of vacuum of the cladded rod-tube assembly before the extrusion step.
 9. The method according to claim 1, further comprising a removing of the clad part after the extrusion step.
 10. The method according to claim 9, wherein the removing of the clad part is an etching-off.
 11. The method according to claim 1, further comprising a wire drawing of the composite wire after the extrusion step.
 12. The method according to claim 1, further comprising a deforming of the composite wire into a coil.
 13. The method according to claim 1, further comprising an annealing of the composite wire after the etching-off step.
 14. A composite wire manufactured by a method of claim
 1. 15. A medical device comprising a composite wire of claim 1 as a lead. 